The present invention relates to linear motors of the type comprised of two parallel ferromagnetic bars connected to a magnetic system, with a coil arrangement being mounted for movement along the lengths of the two bars, the coil arrangement being energized by current and cutting through the magnetic field lines emanating from the bars. Such linear motors are, for example, employed as drive mechanisms for peripheral equipment in data processing applications.
One linear motor of this type (disclosed in Federal Republic of Germany published patent application DT-OS No. 2,309,750) includes a magnet provided at at least one end of the two ferromagnetic bars. This magnet establishes a magnetic field of well-defined orientation between the bars. An energized coil is guided for longitudinal movement along the space intermediate the two bars. With this known construction, a considerable amount of electrical drive energy is wasted for each unit of motive force generated, because only a small part of the conductors constituting the coil, or more precisely only the current flowing through this small part of the coil, actually contributes to the generation of motive force. Also, with this construction, the cross-sectional area of the flux-conducting iron of the magnetic system of the motor must be rather large, because otherwise the flux-conducting iron will quickly saturate magnetically.
In another known construction of this type (disclosed in U.S. Pat. No. 3,899,699), a bar-shaped permanent magnet is mounted at the bottom and extends along the length of a channel formed by an elongated iron flux-return structure of U-shaped cross section. The elongated permanent magnet is magnetized in a direction perpendicular to its elongation and parallel to the two sides of the U of the channel. Arranged within the channel, and extending along its length, is a ferromagnetic rod surrounded by an energized cylindrical coil mounted on a longitudinally shiftable carriage the ferromagnetic material of which also serves as a flux-return structure for completing the magnetic circuitry of the magnetic system. Even with this construction, at most only one half of the energized coil participates electromagnetically in the generation of motive force. Furthermore, the flux of the magnetic system flows through the ferromagnetic material of the carriage on which the coil is mounted, so that this carriage must be sizable and heavy to carry the flux of the magnetic system of the motor.